Unloader means for a reciprocating compressor



Oct. 18, 1960 J c o s 2,956,729

UNLOADER MEANS FOR A RECIPROCATING COMPRESSOR Filed May 14, 1959 2 Sheets-Sheet l ANDREW J'. NICHOLAS INVENTOR.

Oct- 18, 96 A. J. NICHOLAS UNLOAISER MEANS FOR A RECIPROCATING COMPRESSOR Filed May 14, 1959 2 Sheets-Sheet 2 FIG.3

FIG. 4

S A L O H E N I W E R D N A FIG.5

UNLOADER MEANS FOR A RECIPROCATING COMPRESSOR Andrew J. Nicholas, Sutfield, Conn., assignor to Worthington Corporation, Harrison, N.J., a corporation of Delaware Filed May 14, '1959, Ser. No. 813,116

'6 Claims. (Cl. 230-30) This invention relates to a reciprocating compressor of the type utilized in a refrigeration system and more particularly to a hydraulic operated unloader means associ ated with the compressor to vary the capacity thereof.

Various prior art devices have been developed for adjusting the capacity of such compressors. One such unloader is shown in the application of Daniel H. Bobis, Henri Soumerai and Andrew J. Nicholas, Serial No. 741,254, filed June 11, 1958. The foregoing application discloses an unloader of very simple design including first and second annular elements disposed about the cylinder of a reciprocating compressor so that the second element is movable relative the first. A connector means is associated with the movable element to provide fluid communication between a pressure fluid chamber formed between the above elements and any available fluid source such as the lubrication system of the compressor. These prior art devices, however, present many difiiculties both in actual assembly during the manufacture of the compressor, and particularly during the operation of the compressor in a refrigeration system. By way of example, after a period of compressor operation there was noticed an undesirable rattle in the compressor valve service. This was particularly discernible when the unloader means was in the unloaded position. It was found that the passage of gas to and from the cylinder caused the first annular element in devices of the type described hereinabove to vibrate and thereforcause an undesirable chatter.

Accordingly it is an object of the present invention to provide means for an unloader of the type described hereinabove which overcome the vibrations and therefore provide quiet and smooth compressor operation.

It is a further object to accomplish the above objective with the provision of a means which can be manufactured at low cost and is easily removed as a part of the unloader assembly when disassembly is necessary.

It is another object of the present invention to provide a simple, practical and positive unloading mechanism for reciprocating compressors. v

With these and other objects in view, as may appear from the accompanying specification, the invention consists of various features of construction and combination of parts, which will be first described in connection with the accompanying drawings, and the features forming the invention will be specifically pointed out in the claims.

In the drawings:

Figure l is a fragmentary vertical section showing the improved unloader means contemplated by this invention.

Figure 2 is an enlarged fragmentary vertical section showing a modified noise reducing means contemplated by this invention.

Figure 3 is an enlarged fragmentary vertical section the casing generally designated 1 of a reciprocating compressor. A partition 2 taking the form of a lower bulkhead divides the casing into a compression compartment 3, wherein the compressor, as is well known in the art, acts on the gases utilized in the refrigeration system and a crankcase compartment 4 usually containing the driving components (not shown) of the compressor.

While Figure 1 illustrates only one cylinder, it will be understood by those familiar with this art that the present arrangement may be used in single or multi-cylinder reciprocating compressors. One such application in multicylinder compressors may be realized from the teachings of the above mentioned application Serial No. 741,254.

Broadly Figure 1 shows an elongated cylindrical liner 5 having a flange 6 disposed about its upper end. The outer end of the flange is shown as having a sliding fit with the opening 7 formed in the upper portion of the casing 1. The lower end of the cylinder liner 5 has a slip fit with opening 8 in the partition 2 which is of lesser diameter but in alignment with the opening 7.

The liner 5 is retained in operating position through connection with the valve service generally designated 9 by any type of connecting means, such as bolts (not shown), utilized in the art for accomplishing thisobjective. One such arrangement is shown in the above application Serial No. 741,254.

A piston 10 is accommodated by the cylinder 11 formed by the liner 5 and is adapted for reciprocation in conventional manner by a suitable prime mover (not shown) such as a constant speed motor.

Inwardly of the periphery of the flange 6 is formed a plurality of circumferentially spaced suction inlet ports 12 in order to provide communication between the portion of the casing 1 forming the suction manifold shown generally at 13 and the cylinder 11. Accordingly gas will flow from the manifold 13 through ports 12 to the cylinder 11 in accordance with the position of an annular suction valve strip 14 which is disposed in the valve service and held in position by suction valve springs 15 as is clearly shown in the drawings.

A discharge chamber 16 communicates with thecylinder 11 and the usual discharge manifold through the customary discharge valve and port arrangement as is described in detail in the co-pending application mentioned above. g e

When the compressor is loaded downward movement of the piston 10 causes the discharge valve strip 17 to close and prevent a backup of gas from the discharge manifold 16 into the cylinder 11. During this phase of piston travel, as is well known in the art, the suction valve 14 opens and permits gas flow into the cylinder 11. After the piston reaches bottom dead center and starts to move upwardly the compressor compresses the fluid in the cylinder causing the annular suction valve strip-to ,close the suction inlet ports 12 and the discharge valve to open to permit the expulsion of compressed gases out into the discharge manifold through the usual discharge valve service and from there to its contemplated use in the refrigeration system.

In order to operate the compressor at substantially constant speed-but at increments of its full capacity one or more of the suction valve strips 14 are held in an open or unloaded position so that the cylinder associated with this valve strip will be unable to deliver compressed gas to the discharge manifold as above described.

Thisis accomplished by the unloader means generally designated 20 ancl shown inthe drawings as mounted about and relative to the cylinder liner 5 and fitting in an annular groove 21 formed in the partition 2 and about the opening 8. The unloader means is guided and aligned during the assembly of the various elements by means of a fluid supply connector 22 which is connected 3 to a source of fluid, the pressure of which may be varied, such as the lubrication system of the compressor.

The unloader assembly coacts with a plurality of suction valve strip lifting pins 23, referred to as actuating means, which are circumferentially disposed about the cylinder liner 5 and mounted for sliding movement in the corresponding suction inlet ports 12, the pins having sufficient length to hold the valve 14 in open position when the first or movable element 24 of the unloading means 20 engages the head of the pins 23 as hereinafter described.

Springs 25 are mounted about each of the pins 23 between the inner or lower face of the flange 6 and the head of the pin 23. In loaded position the springs will move and hold the pins out of engagement with the valve strip 14 and will be compressed when the compressor is in the unloaded position to coact in holding the valve strip 14 in open position.

The unloader assembly is of relatively simple construction. An example is shown in Figure l of the drawings. It comprises broadly first or outer and second or inner annular elements 24 and 26, having shoulders 27 and 28 formed on the central inner portions thereof, and are mounted about the liner 5 to form a fluid tight chamber therebetween. One of the elements is disposed in movable relation with respect to the other element. In the form shown in Figure 1, and by way of example, the first or outer element 24 is movable with respect to the second element 26. And in order to preclude possible interferences during assembly or disassembly clearance 30 is provided between the element 26 which is mounted on the liner 5, as is described in detail in the above mentioned application, by snap ring 31. A source of fluid, such as from the lubricating system of the compressor, is operatively connected with the chamber 29 through the connector 22 which is mounted in association with the movable element 24. The movable element of course functions to actuate the pins 23 to load or unload the valve 14 depending upon whether fluid is supplied to or removed from the fluid chamber 29.

As was mentioned hereinabove passage of gas to or from the cylinder 11 has a disturbing aflect on the above discribed unloader. More specifically it is belived that this gas action causes the second element 26 to vibrate during operation of the compressor through the distance provided by clearance 30.

In order to arrest this vibration which is more pronounced when the cylinder is in the unloaded position and provide for quiet operation, a resilient means 50,

taking the form of a waved washer purchasable on the open market, is mounted about the element 26 and held in position by shoulders 27 and 28. Accordingly during upward movement of the first element 24 shoulder 28 compresses the means 50 to hold the second element 26 in fixed relation with respect to the cylinder 11.

With the above described construction applicant substantially reduces the vibrations that were present in prior machines embodying unloaders of the type described hereinabove. It will be noted that the unloader means is still removable with the liner as a unit and that provision of a waved washer to eliminate vibrations does not in any way detract from this cartridge feature of the unloader.

Figure 2 shows another form of the invention which diflers from the form shown in Figure 1 only insofar as a waved snap ring 60 is mounted about the liner 5 and in the clearance 30 to provide the function of the washer 50 shown in Figure 1. Removability of ring 60 with the unloader unit is provided for by including a groove 61 in the liner 5. Accordingly upon disassembly the ring 60 will snap into groove 61 and be removable with liner 5.

Figure 3 shows another modified form of the invention; elimination of the vibration of element 26 is provided for by snap ring 60 mounted on an internal flange 70 provided on element 24 and in abutment with the base 71 of element 26. The flange 70 functions as a support for ring 60 and accordingly holds same when it is necessary to remove the unloader as a unit.

It will be understood that the invention is not to be limited to the specific construction or arrangement of parts shown but that they may be widely modified within the invention defined by the claims.

What is claimed is:

1. A cartridge type unloader means for varying the capacity of a reciprocating compressor having a casing including an upper and lower partition dividing the easing into discharge suction and crankcase compartments, a cylinder liner in the casing and mounted between the upper and lower partition, a suction inlet and discharge outlet for said cylinder liner, suction and discharge valve means disposed respectively on the suction inlet and discharge outlet, said unloader means comprising an inner annular element disposed about said cylinder liner, means for connecting the inner annular element to the cylinder liner to maintain same substantially rigidly connected to the cylinder liner and at a predetermined distance from said lower partition, an outer annular element movably mounted about the inner annular element and forming a fluid tight chamber therewith, actuating means on said outer annular element and normally abutting said suction valve means to maintain same in open position, fiuid supply means connected to the fluid tight chamber to move said outer annular element to move the actuating means out of abutment with the suction valve means, resilient means about the cylinder liner and abutting the inner annular element and coacting with the means for connecting said inner element to the cylinder liner to maintain the inner element in fixed position relative said cylinder liner, and support means in the unloader means for engaging said resilient means during disassembly of the unloader means.

2. The unloader means in claim 1 wherein the resilient means comprises a waved washer and the support means for holding same during disassembly comprises coacting shoulders formed on the inner and outer annular elements.

3. The unloader means in claim 1 including a clearance formed by the inner and outer annular elements, the cylinder liner and the lower partition and said resilient means being disposed in said clearance.

4. The unloader means in claim 1 including a clearance formed by the inner and outer annular elements and the cylinder liner means and said resilient means being disposed therein, and the support means for engaging the resilient means. comprises an internal flange formed on the outer annular element.

5. The unloader means in claim 3 wherein the support means for engaging the resilient means comprises a groove in the cylinder liner.

6. The unloader in claim 5 wherein the resilient means comprises a waved snap ring.

References Cited in the file of this patent UNITED STATES PATENTS 2,156,943 Heller May 2, 1939 2,427,638 Vilter et al. Sept. 16, 1947 2,555,004 Rinehart May 29, 1951 2,555,005 Warneke May 29, 1951 2,673,025 Labus et a1 Mar. 23, 1954 2,836,345 Gerteis May 27, 1958 

